High quality sound reproduction is commonly desired in present day computer systems. Many manufacturers offer speaker systems designed specifically for desktop computers. These systems can provide high volume and accurate reproduction across most of the human audible sound spectrum and typically employ conventional, electromagnetic speakers. Such speakers consist of a few electromagnetic speaker elements in an enclosure. The speaker elements are based on audio transducers, which utilize conical or other three-dimensional vibrating members. Conventional, electromagnetic speakers tend to be bulky or heavy.
Desktop computer speaker systems are typically too large, heavy, and fragile for portable use. Due to space and weight constraints, portable computers--which include variants such as laptops, notebooks, PDAs and so on--typically are equipped with small, conventional electromagnetic speakers built into the computer's enclosure. These small, conventional speakers provide poor sound reproduction; their volume and reproduction of the audible spectrum are limited. Poor stereo separation is typical of portable computers due to the limited physical separation achievable for built-in speakers. In spite of these constraints, there exists an increasing demand for high quality, stereo sound reproduction in portable computer systems. Computer users increasingly choose portable computers for the convenience of a small, moveable system while traditional portable computer users, e.g. business travelers, continue to desire good sound reproduction for such applications as audio-visual presentations.
Because thinness is a desirable feature in portable computer configurations, use of speakers comprising a thin enclosure and good sound quality would be one approach to mitigate the portability problem of a computer system with good sound reproduction. Existing thin speakers, generally called "planar speakers", are usually based on two basic design types; electromagnetic and electrostatic. An electromagnetic planar speaker typically possesses a large, flat diaphragm and a set of relatively strong, permanent, strip magnets. The diaphragm is susceptible to tearing. An electrostatic planar speaker employs a very high voltage, which causes a susceptibility to arcing. Over time, arcing can destroy the electrostatic speaker's diaphragm. Though planar speakers of a size suitable for portability can be produced by either of these existing approaches, such speakers would be expensive and lack the reliability of conventional electromagnetic speakers.
The additional problem of good stereo separation in portable computer systems can be solved by placing two speakers, i.e. the left and right sound reproduction channels, at some distance to either side of the portable computer. This complicates the problem of portability, however, because portable computer systems must be compact. A solution to the problem of stereo separation is desirable.